Apparatus and a method of inspecting a turbomachine

ABSTRACT

An apparatus for inspecting a turbomachine includes a plurality of boroscopes, a device to rotate the rotor of the turbomachine and a processor having reference measurements of the rotor blades and/or reference measurements between the rotor blades and the boroscopes. A boroscope is inserted in a casing aperture upstream of the blades to view the leading edge and a portion of one of the surfaces of each blade as the rotor is rotated. A boroscope is inserted in a casing aperture downstream of the blades to view the trailing edge and a portion of one of the surfaces of each blade as the rotor is rotated. The boroscopes supply the images of each of the blades to the processor. The processor analyses the images of the blades and uses the reference measurements to determine the position and size of any defect on any of the rotor blades.

The present invention relates to an apparatus and a method of inspectinga turbomachine and in particular to an apparatus and a method ofinspecting a gas turbine engine.

Currently in-situ inspection of a gas turbine engine takes place using amanually controlled flexible videoscope. In the inspection process theflexible videoscope is inserted through an inspection aperture in acasing of the gas turbine engine and manipulated such that the flexiblevideoscope is able to view the rotor blades of a stage of rotor bladesof the gas turbine engine. Images are taken of interesting features, i.edamage, on the rotor blades or of random rotor blades to illustrate thelevel of contamination or generic degradation of the rotor blades. Thetip of the videoscope is attached to a flexible insertion tube that maybe articulated remotely by an operator who feeds the insertion tubethrough the inspection aperture in the casing of the gas turbine engine.The flexible videoscope is then inserted through another inspectionaperture in the casing of the gas turbine engine and manipulated suchthat the flexible videoscope is able to view the rotor blades of anotherstage of rotor blades of the gas turbine engine. The images are analysedto determine whether to repair damage to the engine, remove the engineor allow continued operation of the engine.

Currently the time to carry out an in-situ inspection of a gas turbineengine is about 8 to 10 hours. The inspection process requires highlyskilled operators to perform the inspection process. During the analysisof the images the operators often have difficulty determining whichcomponent the images relate to.

UK patent GB1296534 discloses a method of inspecting the stator vanes ofa gas turbine engine using a boroscope. The distal end of the boroscopeis provided with an inflatable bag. The boroscope is inserted into thegas turbine engine through an aperture in a casing and after theboroscope has been inserted into the gas turbine engine the bag isinflated between two adjacent rotor blades located on a rotor of the gasturbine engine such that the bag grips and locates the distal end of theboroscope between the rotor blades. The rotor is then rotated to movethe boroscope from stator vane to stator vane so that the boroscope isable to view the edges of the stator vanes of the gas turbine engine.

UK patent application GB2033973A discloses a method of inspecting thestator vanes and/or rotor blades of a gas turbine engine using aboroscope. A shaped guide tube is inserted into the gas turbine enginethrough an aperture in a casing and a distal end of the guide tube ispositioned adjacent a stator vane or a rotor blade to be viewed. Aboroscope is guided by the guide tube to the stator vane or rotor blade.The guide tube is moved radially so that the boroscope is able to viewthe full radial span of the stator vane or rotor blade. All of the rotorblades are inspected by rotating the rotor so that each rotor bladepasses in front of the boroscope. All of the stator vanes are inspectedby positioning the guide tube in other suitable apertures in the casing.

European patent application EP2119875A2 discloses a method of inspectingstationary components, stator vanes, of a gas turbine engine using aninspection element. The inspection element is positioned on a rotor ofthe gas turbine engine. The rotor is rotated so that the inspectionelement is able to view the stationary components. Data is transmittedvia a wireless link from the inspection element. The inspection elementmay be a boroscope or a camera.

Accordingly the present invention seeks to provide an apparatus andmethod of inspecting a turbomachine which reduces, preferably overcomes,the above mentioned problems.

Accordingly the present invention provides a method of inspecting aturbomachine, the turbomachine comprising a rotor having at least onestage of rotor blades and a casing surrounding the rotor and at leastone stage of rotor blades, each rotor blade comprising a platformportion and an aerofoil portion, the aerofoil portion having a leadingedge, a trailing edge, a concave surface, a convex surface and a tip,the method comprising the steps of a) providing a plurality ofboroscopes, b) inserting each boroscope through a respective one of aplurality of apertures in a casing of the turbomachine, at least one ofthe apertures in the casing being upstream of the rotor blades, at leastone of the apertures in the casing being downstream of the rotor blades,c) rotating the rotor of the turbomachine, d) providing referencemeasurements of the rotor blades and/or reference measurements betweenthe rotor blades and the boroscopes, e) viewing the leading edge and atleast a portion of the concave surface or viewing the leading edge andat least a portion of the convex surface of each of the rotor blades ofthe turbomachine as the rotor is rotated using the boroscope in the atleast one of the apertures in the casing upstream of the rotor bladesand supplying the image of each of the rotor blades to the processor, f)viewing the trailing edge and at least a portion of the convex surfaceor viewing the trailing edge and at least a portion of the concavesurface of each of the rotor blades of the turbomachine as the rotor isrotated using the boroscope in the at least one of the apertures in thecasing downstream of the rotor blades and supplying the image of each ofthe rotor blades to the processor, and g) analysing the images of therotor blades and using the reference measurements of the rotor bladesand/or reference measurements between the rotor blades and theboroscopes to determine the position and size of any defect on any ofthe rotor blades.

The reference measurements of the rotor blades may be the measurementfrom the platform portion to the tip of the aerofoil portion of therotor blade and/or the measurement from the leading edge to the trailingedge of the aerofoil portion of the rotor blade.

The method may comprise providing a model of the rotor and the at leastone stage of rotor blades.

The method may comprise placing the image of the leading edge and atleast a portion of the concave surface or placing the image of theleading edge and at least a portion of the convex surface of each of therotor blades of the turbomachine onto corresponding positions of themodel of the rotor and rotor blades and placing the image of thetrailing edge and at least a portion of the convex surface or placingthe image of the trailing edge and at least a portion of the concavesurface of each of the rotor blades of the turbomachine ontocorresponding positions of the model of the rotor and rotor blades.

Each boroscope may comprise a rigid structure and at least one cameraarranged at a predetermined longitudinal position, the at least onecamera is arranged with a line of sight transverse to the longitudinaldirection of the boroscope.

At least one of the boroscopes may comprise a plurality of cameras. Aplurality of boroscopes may comprise a plurality of cameras.

At least one of the boroscopes may comprise a plurality of cameras atthe predetermined longitudinal position and the cameras are arrangedwith lines of sight arranged at different angles. A plurality of theboroscopes may comprise a plurality of cameras at the predeterminedlongitudinal position and the cameras are arranged with lines of sightarranged at different angles.

At least one of the boroscopes may comprise a plurality of cameras atdifferent longitudinal positions. A plurality of the boroscopes maycomprise a plurality of cameras at different longitudinal positions.

The method may comprise supplying the image of each of the rotor bladesfrom each of the cameras at the different longitudinal positions of theboroscope to the processor, the processor producing a composite image ofeach of the rotor blades from the images supplied by the plurality ofcameras.

The method may comprise placing the composite image of each of the rotorblades of the turbomachine onto corresponding positions of the model ofthe rotor and rotor blades.

At least one of the boroscopes may comprise at least one camera arrangedwith a line of sight directed in a downstream direction towards a stageof rotor blades and at least one camera arranged with a line of sightdirected in an upstream direction towards a stage of rotor blades. Aplurality of the boroscopes may comprise at least one camera arrangedwith a line of sight directed in a downstream direction towards a stageof rotor blades and at least one camera arranged with a line of sightdirected in an upstream direction towards a stage of rotor blades.

At least one of the boroscopes may comprise a plurality of cameras atdifferent longitudinal positions arranged with a line of sight directedin the downstream direction towards a stage of rotor blades and aplurality of cameras at different longitudinal positions arranged with aline of sight in the upstream direction towards a stage of rotor blades.

The method may comprise providing a measurement of the angular positionof the rotor relative to the boroscopes, supplying the measurement ofthe angular position of the rotor to the processor and relating theimages of each of the rotor blades to the corresponding rotor blade onthe rotor.

The turbomachine may comprise a stage of stator vanes upstream of the atleast one stage of rotor blades and a stage of stator vanes downstreamof the at least one stage of rotor blades, step b) comprising insertinga boroscope between two adjacent stator vanes of the stage of statorvanes upstream of the at least one stage of rotor blade and inserting aboroscope between two adjacent stator vanes of the stage of stator vanesdownstream of the at least one stage of rotor blades.

Step b) may comprise placing a boroscope upstream of each one of aplurality of stages of rotor blades and placing a boroscope downstreamof each one of the plurality of stages of rotor blades, step d)comprises providing reference measurements of the rotor blades of eachof the stages of rotor blades and/or reference measurements between therotor blades of each of the stages of rotor blades and the correspondingboroscopes and step g) comprises analysing the images of the rotorblades of each of the stages of rotor blades and using the referencemeasurements of the rotor blades for each stage of rotor blades and/orreference measurements between the rotor blades of each stage of rotorblades and the corresponding boroscopes to determine the position andsize of any defect on any of the rotor blades.

Step b) may comprise placing a single boroscope upstream of a stage ofrotor blades and downstream of a stage of rotor blades, step e)comprises viewing the leading edge and at least a portion of the concavesurface or viewing the leading edge and at least a portion of the convexsurface of each of the rotor blades of the stage of rotor bladesdownstream of the boroscope as the rotor is rotated using the boroscopeand supplying the image of each of the rotor blades to the processor,and step f) comprises viewing the trailing edge and at least a portionof the convex surface or viewing the trailing edge and at least aportion of the concave surface of each of the rotor blades upstream ofthe boroscope as the rotor is rotated using the boroscope and supplyingthe image of each of the rotor blades to the processor.

The rotor may be a compressor rotor and the rotor blades are compressorblades.

The rotor may be a turbine rotor and the rotor blades are turbineblades.

The turbomachine may be a gas turbine engine. The turbomachine may be asteam turbine or a water turbine.

The present invention also provides a method of inspecting aturbomachine, the turbomachine comprising a rotor having at least onestage of rotor blades and a casing surrounding the rotor and at leastone stage of rotor blades, each rotor blade comprising a platformportion and an aerofoil portion, the aerofoil portion having a leadingedge, a trailing edge, a concave surface, a convex surface and a tip,the method comprising the steps of a) providing a plurality ofboroscopes, b) inserting each boroscope through a respective one of aplurality of apertures in a casing of the turbomachine, at least one ofthe apertures in the casing being upstream of the rotor blades, at leastone of the apertures in the casing being downstream of the rotor blades,c) rotating the rotor of the turbomachine, d) providing a processorhaving a model of the rotor and the at least one stage of rotor blades,e) viewing the leading edge and at least a portion of the concavesurface or viewing the leading edge and at least a portion of the convexsurface of each of the rotor blades of the turbomachine as the rotor isrotated using the boroscope in the at least one of the apertures in thecasing upstream of the rotor blades and supplying the image of each ofthe rotor blades to the processor, f) viewing the trailing edge and atleast a portion of the convex surface or viewing the trailing edge andat least a portion of the concave surface of each of the rotor blades ofthe turbomachine as the rotor is rotated using the boroscope in the atleast one of the apertures in the casing downstream of the rotor bladesand supplying the image of each of the rotor blades to the processor,and g) placing the image of the leading edge and at least a portion ofthe concave surface or the leading edge and at least a portion of theconvex surface of each of the rotor blades of the turbomachine ontocorresponding positions of the model of the rotor and rotor blades andplacing the image of the trailing edge and at least a portion of theconvex surface or the trailing edge and at least a portion of theconcave surface of each of the rotor blades of the turbomachine ontocorresponding positions of the model of the rotor and rotor blades.

The present invention also provides an apparatus for inspecting aturbomachine, the turbomachine comprising a rotor having at least onestage of rotor blades and a casing surrounding the rotor and at leastone stage of rotor blades, each rotor blade comprising a platformportion and an aerofoil portion, the aerofoil portion having a leadingedge, a trailing edge, a concave surface, a convex surface and a tip,the casing of the turbomachine having a plurality of apertures, at leastone of the apertures in the casing being upstream of the rotor bladesand at least one of the apertures in the casing being downstream of therotor blades,

-   -   the apparatus comprising a plurality of boroscopes, each        boroscope being insertable through a respective one of the        plurality of apertures in the casing of the turbomachine,    -   a device to rotate the rotor of the turbomachine,    -   a processor having reference measurements of the rotor blades        and/or reference measurements between the rotor blades and the        boroscopes,    -   at least one of the boroscopes inserted in at least one of the        apertures in the casing upstream of the rotor blades being        arranged to view the leading edge and at least a portion of the        concave surface or being arranged to view the leading edge and        at least a portion of the convex surface of each of the rotor        blades of the turbomachine as the rotor is rotated,    -   the at least one of the boroscopes being arranged to supply the        image of the leading edge and at least a portion of the concave        surface or being arranged to supply the image of the leading        edge and at least a portion of the convex surface of each of the        rotor blades of the turbomachine as the rotor is rotated,    -   at least one of the boroscopes inserted in at least one of the        apertures in the casing downstream of the rotor blades being        arranged to view trailing edge and at least a portion of the        convex surface or being arranged to view the trailing edge and        at least a portion of the concave surface of each of the rotor        blades of the turbomachine as the rotor is rotated,    -   the at least one of the boroscopes being arranged to supply the        image of the trailing edge and at least a portion of the convex        surface or being arranged to supply the image of the trailing        edge and at least a portion of the concave surface of each of        the rotor blades of the turbomachine as the rotor is rotated,    -   the processor being arranged to analyse the images of the rotor        blades and to use the reference measurements of the rotor blades        and/or reference measurements between the rotor blades and the        boroscopes to determine the position and size of any defect on        any of the rotor blades.

The present invention also provides a boroscope comprising a rigidstructure and a plurality of cameras, each camera is arranged at apredetermined longitudinal position, each camera is arranged with a lineof sight transverse to the longitudinal direction of the boroscope.

The boroscope may comprise a plurality of cameras at the predeterminedlongitudinal position and the cameras are arranged with lines of sightarranged at different angles.

The boroscope may comprise a plurality of cameras at differentlongitudinal positions.

The boroscope may comprise at least one camera arranged with a line ofsight directed in a first direction and at least one camera arrangedwith a line of sight directed in a second direction opposite to thefirst direction.

The boroscope may comprise a plurality of cameras at differentlongitudinal positions arranged with a line of sight in the firstdirection and a plurality of cameras at different longitudinal positionsarranged with a line of sight in the second direction.

The present invention will be more fully described with reference to theaccompanying drawings, in which:

FIG. 1 is a cross-sectional view through a turbofan gas turbine engine.

FIG. 2 is an enlarged cross-sectional view through an intermediatepressure compressor of the turbofan gas turbine engine shown in FIG. 1and an apparatus for inspecting a gas turbine engine according to thepresent invention.

FIG. 3 is a further enlarged view of a portion of the intermediatepressure compressor and one of the boroscopes of the apparatus forinspecting a gas turbine engine according to the present invention.

FIG. 4 is a cross-sectional view in the direction of arrows A-A in FIG.3.

FIG. 5 is an alternative cross-sectional view in the direction of arrowsA-A in FIG. 3.

FIG. 6 is a view of a first type of boroscope of the apparatus forinspecting a gas turbine engine according to the present invention.

FIG. 7 is a view of a second type of boroscope of the apparatus forinspecting a gas turbine engine according to the present invention.

FIG. 8 is a view of an alternative third type of boroscope of theapparatus for inspecting a gas turbine engine according to the presentinvention.

FIG. 9 is a view of a third type of boroscope of the apparatus forinspecting a gas turbine engine according to the present invention.

A turbofan gas turbine engine 10, as shown in FIG. 1, comprises in flowseries an inlet 12, a fan section 14, a compressor section 16, acombustion section 18, a turbine section 20 and an exhaust 22. The fansection 14 comprises a fan 24. The compressor section 16 comprises inflow series an intermediate pressure compressor 26 and a high pressurecompressor 28. The turbine section 20 comprises in flow series a highpressure turbine 30, an intermediate pressure turbine 32 and a lowpressure turbine 34. The fan 24 is driven by the low pressure turbine 34via a shaft 40. The intermediate pressure compressor 26 is driven by theintermediate pressure turbine 32 via a shaft 38 and the high pressurecompressor 28 is driven by the high pressure turbine 30 via a shaft 36.The turbofan gas turbine engine 10 operates quite conventionally and itsoperation will not be discussed further. The turbofan gas turbine engine10 has a rotational axis X.

The intermediate pressure compressor 26, as shown in FIG. 2, comprises arotor 50 having a plurality of axially spaced stages 51A, 51B, 51C, 51D,51E and 51F of rotor blades 52. The rotor blades 52 in each stage 51A,51B, 51C, 51D, 51E and 51F of rotor blades 52 are circumferentiallyspaced and extend radially outwardly from the rotor 50. Each rotor blade52 comprises a root portion 51, a platform portion 53 and an aerofoilportion 54. The aerofoil portion 54 of each rotor blade 50 comprises aleading edge 55, a trailing edge 57, a concave surface 59, a convexsurface 61 and a tip 63. The root portion 54 of each rotor blade 52 mayhave a dovetail shape or a firtree shape. The root potion 54 of eachrotor blade 52 locates in a groove 58 in the rim 56 of the rotor 50. Ifthe root portions 54 of all of the rotor blades 52 in a stage 51A, 51B,51C, 51D, 51E and 51F of rotor blades have a dovetail shape then theroot portions 54 of all the rotor blades 52 locate in acircumferentially extending, dovetail shape, groove 58 in the rim 56 ofthe rotor 50. If the root portions 54 of all of the rotor blades 52 in astage 51A, 51B, 51C, 51D, 51E and 51F of rotor blades have a firtreeshape then the root portion 54 of each rotor blade 52 locates in acorresponding one of a plurality of circumferentially spaced, axiallyextending, firtree shape, grooves 58 in the rim 56 of the rotor 50.

The intermediate pressure compressor 26 also comprises an inner casing60 surrounding the rotor 50 and rotor blades 52 and an outer casing 62surrounding the inner casing 60. The inner casing 60 carries a pluralityof axially spaced stages 63A, 63B, 63C, 63D, 63E, 63F and 63G of statorvanes 64. The stator vanes 64 in each stage 63A, 63B, 63C, 63D, 63E, 63Fand 63G of stator vanes 64 are circumferentially spaced and extendradially inwardly from the inner casing 60. The radially outer ends ofthe stator vanes 64 of each stage 63A, 63B, 63C, 63D, 63E, 63F and 63Gof stator vanes 64 are secured to the inner casing 60. The stages 51A,51B, 51C, 51D, 51E and 51F of rotor blades 52 and the stages 63A, 63B,63C, 63D, 63E, 63F and 63G of stator vanes 64 are arranged axiallyalternately through the intermediate pressure compressor 26. The innercasing 60 and the outer casing 62 have a plurality of aligned, e.g.coaxial, inspection apertures 66 and 68 respectively. At least one pairof aligned apertures 66 and 68 is arranged axially between a respectivepair of axially adjacent stages 51A and 51B or 51B and 51C of rotorblades 52 and circumferentially between an adjacent pair of stator vanes64 in the stage 63B of stator vanes 64 between the axially adjacentstages 51A, 51B or 51B, 51C of rotor blades 62. In addition one pair ofaligned apertures 66 and 68 is arranged axially upstream of the axiallyupstream stage, the first stage 51A, of rotor blades 52 andcircumferentially between an adjacent pair of stator vanes 64 in thestage 63A of stator vanes 64 upstream of the axially upstream stage 51Aof rotor blades 62. In addition one pair of aligned apertures 66 and 68is arranged axially downstream of the axially downstream stage, the laststage, 51F of rotor blades 52 and circumferentially between an adjacentpair of stator vanes 64 in the last stage 63G of stator vanes 64downstream of the axially downstream stage 51F of rotor blades 62.

FIGS. 2 to 4 also show an apparatus 69 for inspecting the gas turbineengine 10. The apparatus 69 comprises a plurality of boroscopes 70 andeach boroscope 70 is located in a respective one of the pairs of alignedapertures 66 and 68 in the inner and outer casings 60 and 62respectively. Each of the boroscopes 70 comprises a rigid structure 72and at least one camera 74. Each of the boroscopes 70 is secured to theouter casing 62 while it is in the associated aperture 68 in the outercasing 62, for example each boroscope 70 is fastened to the outer casing62 by bolts locating in threaded holes around the associated aperture68. The at least one camera 74 is arranged at a predeterminedlongitudinal position and the at least one camera 74 is arranged with aline of sight transverse to the longitudinal direction of the boroscope70. Each boroscope 70 is unique, and is different to all of the otherboroscopes 70. The boroscope 70 upstream of the first stage, upstreamstage, 51A of rotor blades 52 may have four or five cameras 74 at fouror five predetermined longitudinal positions and each camera 74 isarranged with a line of sight directed in a downstream direction towardsthe first stage, upstream stage, 51A of rotor blades 52, as shown inFIG. 6. The boroscope 70 downstream of the downstream stage, last stage,51F of rotor blades 52 has one camera 74 at a predetermined longitudinalposition and the camera 74 is arranged with a line of sight directed inan upstream direction towards the downstream stage, last stage, 51F ofrotor blades 52, as shown in FIG. 8. Each boroscope 70 positionedbetween a pair of axially adjacent stages 51A and 51B or 51B and 51C ofrotor blades 52 comprises at least one camera 74 arranged with a line ofsight S1 directed in a downstream direction towards a stage 51B or 51Crespectively of rotor blades 52 and at least one camera 74 arranged witha line of sight S2 directed in an upstream direction towards a stage 51Aor 51B respectively of rotor blades 52, as shown in FIG. 7. The numberof cameras 74 on a particular boroscope 74 is determined by the radiallength of the rotor blades 52 and the requirement that the camera, orcameras, produce a full image of the rotor blades 52. Each camera 74 islocated at a predetermined position on the boroscope 70 such that a fullimage of the rotor blades 52 is obtained. Some of the boroscopes 70 maycomprise a plurality of cameras 74 arranged at different longitudinalpositions. Each camera 74 on each boroscope 70 also has an associatedlight source 76 to illuminate the rotor blades 52. The cameras 74 onboroscopes 70 with a plurality of cameras 74 are arranged such that thefields of view of the cameras 74 overlap to ensure that the images ofthe cameras 74 may be amalgamated together to produce a full image ofthe rotor blades 52.

The apparatus 69 also comprises a processor 78, for example a personalcomputer, and each camera 74 of each boroscope 70 is connected to theprocessor 78 by a respective cable 80 so as to supply images from therespective camera 74 to the processor 78. The processor 78 has a store82 containing reference measurements of the rotor blades 52 in eachstage of rotor blades 52 and/or has reference measurements between therotor blades 52 in each stage of rotor blades 52 and the boroscope 70upstream of the stage of rotor blades 52 and/or reference measurementsbetween the rotor blades 52 in each stage of rotor blades 52 and theboroscope 70 downstream of the stage of rotor blades 52. The processor78 has a model 84 of the rotor 50 and each stage of rotor blades 52. Thereference measurements of the rotor blades 52 may be the measurementfrom the platform portion 53 to the tip 63 of the rotor blade 52 for therespective stage of rotor blades 52 and/or the measurement from theleading edge 55 to the trailing edge 57 of the rotor blade 52 for therespective stage of rotor blades 52. The apparatus 69 also comprises asensor 86 which provides a measurement of the angular position of therotor 50 relative to the boroscopes 70 and the measurement of theangular position of the rotor 50 is supplied to the processor 78. Theapparatus 69 additionally comprises a display 88 connected to theprocessor 78. The apparatus 69 further comprises a device 90 arranged torotate the rotor 50.

A method of inspecting a gas turbine engine 10 according to the presentinvention is described with reference to FIGS. 2 to 4. The method ofinspecting the gas turbine engine 10 comprises providing a plurality ofboroscopes 70, inserting each boroscope 70 through a respective one of aplurality of apertures 66, 68 in a casing 62, 64 of the gas turbineengine 10, at least one of the apertures 66, 68 in the casing 62, 64 isupstream of the rotor blades 52 and at least one of the apertures 66, 68in the casing 62, 64 is downstream of the rotor blades 52. The rotor 50of the gas turbine engine 10 is rotated. Reference measurements of therotor blades 52 and/or reference measurements between the rotor blades52 and the boroscopes 70 are provided. The leading edge 55 and at leasta portion of the concave surface 59 or the leading edge 55 and at leasta portion of the convex surface 61 of each of the rotor blades 52 of thegas turbine engine 10 are viewed as the rotor 50 is rotated using theboroscope 70 in the at least one of the apertures 66, 68 in the casing62, 64 upstream of the rotor blades 52 and the image of each of therotor blades 52 is supplied to the processor 78. The trailing edge 57and at least a portion of the convex surface 61 or the trailing edge 57and at least a portion of the concave surface 59 of each of the rotorblades 52 of the gas turbine engine 10 are viewed as the rotor 50 isrotated using the boroscope 70 in the at least one of the apertures 66,68 in the casing 62, 64 downstream of the rotor blades 52 and the imageof each of the rotor blades 52 is supplied to the processor 78. Theprocessor 78 analyses the images of the rotor blades 52 and uses thereference measurements of the rotor blades 52 and/or referencemeasurements between the rotor blades 52 and the boroscopes 70 todetermine the position and size of any defect on any of the rotor blades52.

The processor 78 places the image of the leading edge 55 and at least aportion of the concave surface 59 or places the image of the leadingedge 55 and at least a portion of the convex surface 61 of each of therotor blades 52 of the gas turbine engine 10 onto correspondingpositions of the model of the rotor 50 and rotor blades 52 and placesthe image of the trailing edge 57 and at least a portion of the convexsurface 61 or places the image of the trailing edge 57 and at least aportion of the concave surface 59 of each of the rotor blades 52 of thegas turbine engine 10 onto corresponding positions of the model of therotor 50 and rotor blades 52.

The image of each of the rotor blades 52 from each of the cameras 74 atthe different longitudinal position of the boroscope 70 are supplied tothe processor 78, the processor 78 producing a composite image of eachof the rotor blades 52 from the images supplied by the plurality ofcameras 74. The composite image of each of the rotor blades 52 of thegas turbine engine 10 are placed onto corresponding positions of themodel of the rotor 50 and rotor blades 52.

The processor 78 also analyses the measurement of the angular positionof the rotor 50 relative to the boroscopes 70 provided by the sensor 86and the processor 78 relates the images of each of the rotor blades 52to the corresponding rotor blade 52 on the rotor 50.

The method comprises inserting a boroscope 70 between two adjacentstator vanes 64 of the stage of stator vanes 64 upstream of the at leastone stage of rotor blades 52 and inserting a boroscope 70 between twoadjacent stator vanes 64 of the stage of stator vanes 64 downstream ofthe at least one stage of rotor blades 52. The method comprises placinga boroscope upstream 70 of each one of a plurality of stages of rotorblades 52 and placing a boroscope 70 downstream of each one of theplurality of stages of rotor blades 52 and comprises providing referencemeasurements of the rotor blades 52 of each of the stages of rotorblades 52 and/or reference measurements between the rotor blades 52 ofeach of the stages of rotor blades 52 and the corresponding boroscopes70 and comprises analysing the images of the rotor blades 52 of each ofthe stages of rotor blades 52 and using the reference measurements ofthe rotor blades 52 for each stage of rotor blades 52 and/or referencemeasurements between the rotor blades 52 of each stage of rotor blades52 and the corresponding boroscopes 70 to determine the position andsize of any defect on any of the rotor blades 52.

FIG. 5 shows a boroscope 70 which comprises a plurality of cameras 74 atone or more of the predetermined longitudinal position and the cameras74 are arranged with lines of sight S1, S1′ and S1″ directed in adownstream direction towards a stage 51B or 51C respectively of rotorblades 52 arranged at different angles and cameras 74 are arranged withlines of sight S2, S2′ and S2″ directed in an upstream direction towardsa stage 51A or 51B respectively of rotor blades 52 arranged at differentangles. This arrangement provides a greater amount of viewing capacity.

FIG. 6 shows a first type of boroscope 70A arranged to be insertedupstream of the first stage 51A of rotor blades 52. The boroscope 70A inthis example has four cameras 74, each camera 74 is arranged at arespective one of four predetermined longitudinal positions on theboroscope 70A. Each of the cameras 74 is arranged with a line of sightdirected towards the upstream edge 55 of the first stage, upstreamstage, 51A of rotor blades 52.

FIG. 7 shows a second type of boroscope 70B arranged to be inserteddownstream of the first stage 51A of rotor blades 52 and upstream of thesecond stage 51B of rotor blades 52. The boroscope 70B has seven cameras74. Four of the cameras 74 are arranged with a line of sight directedtowards the downstream edge 57 of the first stage, upstream stage, 51Aof rotor blades 52. Three of the cameras 74 are arranged with a line ofsight directed towards the upstream edge 55 of the second stage,upstream stage, 51B of rotor blades 52. Each camera 74 of the fourcameras 74 with a line of sight directed towards the downstream edge 57of the first stage, upstream stage, 51A of rotor blades 52 is arrangedat a respective one of four predetermined longitudinal positions on theboroscope 70B. Each of the three cameras 74 with a line of sightdirected towards the upstream edge 55 of the second stage 51 B of rotorblades 52 is arranged at a respective one of three predeterminedlongitudinal positions on the boroscope 70B.

FIG. 8 shows another second type of boroscope 70C arranged to beinserted downstream of the one stage 51B of rotor blades 52 and upstreamof another stage 51C of rotor blades 52. The boroscope 70C has sixcameras 74. Three of the cameras 74 are arranged with a line of sightdirected towards the downstream edge 57 of one stage 51B of rotor blades52. Three of the cameras 74 are arranged with a line of sight directedtowards the upstream edge 55 of the other stage 51C of rotor blades 52.Each camera 74 of the three cameras 74 with a line of sight directedtowards the downstream edge 57 of one stage 51B of rotor blades 52 isarranged at a respective one of three predetermined longitudinalpositions on the boroscope 70C. Each of the three cameras 74 with a lineof sight directed towards the upstream edge 55 of the other stage 51C ofrotor blades 52 is arranged at a respective one of three predeterminedlongitudinal positions on the boroscope 70C.

FIG. 9 shows a third type of boroscope 70D arranged to be inserteddownstream of the last stage 51F of rotor blades 52. The boroscope hasone camera 74 arranged at a predetermined longitudinal position on theboroscope 70D. The camera 74 is arranged with a line of sight directedtowards the downstream edge 57 of the last stage, downstream stage, 51Fof rotor blades 52.

The rotor 50 is only rotated through one full revolution so that eachrotor blade 52 in each stage of rotor blades 52 is viewed and is imagedfrom both the leading edge 55 and the trailing edge 57 and a video isrecorded. The present invention allows all the rotor blade stages 52 onthe rotor 50 to be fully inspected within a few minutes of opening thecowling of the turbofan gas turbine engine 10.

In the present invention multiple data streams, e.g. from multiple USBcameras, are plugged into a management hub and inputted as a single datastream into the processor, personal computer. The videos may bedisplayed on a monitor and image analysis software is used to stitch themultiple data streams together to build a complete picture of the rotor,and rotor blades, and highlight any areas of interest, such as areas onany one or more of the rotor blades which has damage or erosion. Themodel in the processor may have the images of the rotor blades from thecameras painted, overlaid, on the surfaces of the corresponding rotorblades in the model in the processor. The use of multiple cameras eachpositioned at a fixed, known, point, together with the rotation of therotor through a full revolution allows measurements to be taken from theimages. Each of the apertures in the outer and inner casings is at afixed, known, point and each of the boroscopes is located in arespective aperture in the outer casing and secured to the outer casingwhile in the respective aperture in the outer casing. Each of thecameras on each boroscope is at a fixed, known, point on the boroscopeand thus the positions of the cameras within the gas turbine engine areknown and the positions of the cameras relative to the rotor blades onthe rotors are known.

Thus, the advantage of the present invention is that it allows anin-situ inspection of a gas turbine engine to be carried out within afew minutes compared to about 8 to 10 hours it currently takes toperform an in-situ inspection. Another advantage of the presentinvention is that the in-situ inspection process does not require highlyskilled operators to perform the inspection process. A further advantageof the present invention is that the analysis of the images makes iteasy for the operators to determine which component the images relateto. Furthermore, the data quality is better than the current in-situinspection process.

The present invention has been described with reference to inspectingthe rotor and rotor blades of the intermediate pressure compressor butthe present invention is equally applicable to inspecting the rotor androtor blades of the high pressure compressor, the rotor and rotor bladesof the high pressure turbine, the rotor and rotor blades of theintermediate pressure turbine or the rotor and rotor blades of the lowpressure turbine. The present invention may be also be used to inspectthe rotor and rotor blades of the intermediate pressure compressor, therotor and rotor blades of the high pressure compressor, the rotor androtor blades of the high pressure turbine, the rotor and rotor blades ofthe intermediate pressure turbine and the rotor and rotor blades of thelow pressure turbine all at the same time. The present invention may bealso be used to inspect the rotor and rotor blades of the high pressurecompressor, the rotor and rotor blades of the high pressure turbine andthe rotor and rotor blades of the low pressure turbine all at the sametime.

Although the present invention has been described with reference toinspecting a turbofan gas turbine engine, the present invention isequally applicable to inspecting a turbojet gas turbine engine, aturboshaft gas turbine engine or a turboprop gas turbine engine. Thepresent invention is applicable to inspecting aero gas turbine engine,marine gas turbine engines or industrial gas turbine engines.

It is also possible to provide each boroscope with a data store and adata processor so that it is possible to do data processing at eachboroscope and then subsequently download the data from each boroscope tothe processor.

Although the present invention has been described with reference toinspecting gas turbine engines the present invention is equallyapplicable to inspecting other types of turbomachine, for example asteam turbine, a water turbine or a wind turbine.

The present invention also provides a method of inspecting aturbomachine, the turbomachine comprising a rotor having at least onestage of rotor blades and a casing surrounding the rotor and at leastone stage of rotor blades, each rotor blade having a leading edge, atrailing edge, a concave surface and a convex surface, the methodcomprising the steps of a) providing a plurality of boroscopes, b)inserting each boroscope through a respective one of a plurality ofapertures in a casing of the turbomachine, at least one of the aperturesin the casing being upstream of the rotor blades, at least one of theapertures in the casing being downstream of the rotor blades, c)rotating the rotor of the turbomachine, d) providing a processor havinga model of the rotor and the at least one stage of rotor blades, e)viewing the leading edge and at least a portion of the concave surfaceor viewing the leading edge and at least a portion of the convex surfaceof each of the rotor blades of the turbomachine as the rotor is rotatedusing the boroscope in the at least one of the apertures in the casingupstream of the rotor blades and supplying the image of each of therotor blades to the processor, f) viewing the trailing edge and at leasta portion of the convex surface or viewing the trailing edge and atleast a portion of the concave surface of each of the rotor blades ofthe turbomachine as the rotor is rotated using the boroscope in the atleast one of the apertures in the casing downstream of the rotor bladesand supplying the image of each of the rotor blades to the processor,and g) placing the image of the leading edge and at least a portion ofthe concave surface or the leading edge and at least a portion of theconvex surface of each of the rotor blades of the turbomachine ontocorresponding positions of the model of the rotor and rotor blades andplacing the image of the trailing edge and at least a portion of theconvex surface or the trailing edge and at least a portion of theconcave surface of each of the rotor blades of the turbomachine ontocorresponding positions of the model of the rotor and rotor blades.

1. A boroscope comprising a rigid structure and a plurality of cameras,each camera is arranged at a predetermined longitudinal position, eachcamera is arranged with a line of sight transverse to the longitudinaldirection of the boroscope.
 2. A boroscope as claimed in claim 1 whereinthe boroscope comprises a plurality of cameras at the predeterminedlongitudinal position and the cameras are arranged with lines of sightarranged at different angles.
 3. A boroscope as claimed in claim 1wherein the boroscope comprises a plurality of cameras at differentlongitudinal positions.
 4. A boroscope as claimed in claim 1 wherein theboroscope comprises at least one camera arranged with a line of sightdirected in a first direction and at least one camera arranged with aline of sight directed in a second direction opposite to the firstdirection.
 5. A boroscope as claimed in claim 4 wherein the boroscopecomprises a plurality of cameras at different longitudinal positionsarranged with a line of sight in the first direction and a plurality ofcameras at different longitudinal positions arranged with a line ofsight in the second direction.